"Prochordates" and chordate characters Flashcards
what are two major animal groups based on embryonic development?
- protosomes
- deuterostomes
protosomes (first mouth)
spiral/offset cleavage, schizocoelom, blastopore forms mouth
deuterostomes (second mouth)
radial/aligned cleavage, enterocoelom, blastopore forms anus
chordates are __________(bilaterally symmetrical) deuterstomes
bilaterian
what are the 6 chordate characteristics?
- notochord
- dorsal hollow nerve cord
- pharyngeal slits
- postanal tail
- endostyle
- myomeres
notochord
longitudinal supporting rod composed of fibrous connective tissue
dorsal hollow nerve cord
situated above the notochord and develops in the central nervous system in vertebrates
pharyngeal slits
series of small openings that pierce the pharynx
postanal tail
posterior extension of the body past the anus used for locomotion
endostyle
(subpharyngeal and thyroid gland) involved in mucus production and/or iodine metabolism
myomeres
muscles block involved with locomotion
T/F: the chordate characteristics may be a permanent adult structure or they can occur temporarily during development
True
are chordate characteristics synapomorphies?
yes
what characteristic allows for lateral flexion but prevents collapse by muscle contraction during locomotion?
Notochord
the notochord consists of a core of _________ encased in a sheath of _______ fibers.
glycoproteins, collagen
what is the notochord largely replaced by in most vertebrates?
vertebral column
the dorsal hollow nerve cord forms the ______ via ___________.
CNS, neurulation
the dorsal hollow nerve chord is induced by?
the notochord
in ___________ the nerved chord is ventrally placed and solid.
non-chordates
how do protochordates intake water and food particles?
water containing suspended food particles enters the mouth and then through the pharynx. the food becomes trapped in the pharyngeal mucus and water exits through the pharyngeal slits
in vertebrates, the pharynx is a part of the _________ and _________.
digestive and respiratory system
in vertebrates, the pharynx develops a series of _________ _______ between the pharyngeal arches during _______ ______.
pharyngeal pouches, embryonic growth
in “fishes” pharyngeal pouches are pierced forming __________
gill slits
pharyngeal slits have an exadaptation for respiratory change which means what?
pharyngeal walls of pouches become vascularized for gas exchange
what is the function of the post-anal tail?
locomotion, counterbalance, and defense
where is the endostyle found in protochordates?
pharyngeal floor
what is the function of the endostyle?
produces mucus to trap food and synthesizes iodine-binding proteins
what is the endostyle homologous to in vertebrates?
sub pharyngeal gland and thyroid gland
what are myomeres?
segmented muscle blocks separated by myosepta
what is the function of myomeres?
locomotion
what do protochordates consost of?
an informal group consisting of hemichordates, cephalochordates, and urochordates
T/F: Protochordates have none of the chordate characteristics
FALSE: protochordate have 1 or more characters that may be permanent in the adult or occur temporarily during development
T/F: protochordate are passive suspension feeders by means of cilia and mucus
TRUE
what phylum are hemichordates a part of?
hemichordata
what are hemichordates?
marine acorn worms
what chordate characteristics do hemichordates (acorn worms) possess?
pharyngeal slits
in hemichordates, what is used for locomotion and feeding?
ciliated proboscis (head of the worm)
in hemichordates (acorn worms) where does water enter and exit?
water enters through the mouth and exits through pharyngeal slits
T/F: hemichordates have a notochord
FALSE!!! they have a stomochord which is used for stability
T/F: hemichordates and echinoderms (sea cucumbers) are sister taxa
TRUE: they branch from a common node and are often considered closely related
T/F: hemichordate larvae closely resemble echinoderm larvae
TRUE
what is the phylum and subphylum of cephalochordates
phylum Chordata, subphylum Cephalochordata
amphioxus (branchiostoma) is a part of what protochordate group?
cephalochordates
cephalochordates are cosmopolitan which means?
they are found all over the place but especially in warm temperate and tropical seas
Do cephalochordates (amphioxus) possess all 6 chordate characteristics?
YES
what does the wheel organ do in cephalochordates (amphioxus)?
draws in water and food particles
what do the buccal cirri and velum do in cephalochordates (amphioxus)?
sorts the water and food particles when entering
what does the hatscheks pit do in cephalochordates (amphioxus)?
secretes mucus and possible endocrine function
how do the food particles make it through the “digestive system” of cephalochordates (amphioxus)?
Food particles trapped in the mucus secreted by the endostyle are moved toward the epibranchial groove vis cilia and sent to the digestive tract and water exits through pharyngeal slits into the atrium and out the atriopore
what is the oldest known chordate? what chordate features did it have?
pikaia gracilens (5 cm long). traces of an elongated notochord, dorsal hollow nerve cord, and myomeres
what are the phylum and subphylum of urochordates?
phylum Chordata, subphylum Urochordata
what are examples of urochordates?
tunicates and ascidian larvae
how many of the chordate characteristics do the ascidian larvae have? adult?
larvae have 5 chordate characteristics (6 including weak myomeres)
adult has 2 characters
ascidian larvae have a post-anal tail designed for?
dispersal (to get away)
what are the adhesive papillae/organs in ascidian larvae used for?
attach to a suitable substrate
what is the statocyst used for in ascidian larvae?
senses gravity
what is the ocellus used for in ascidian larvae?
photoreception
T/F: ascidian larvae have a well-developed digestive system
FALSE!! they have a poorly developed digestive system
what happens when the ascidian larvae go through metamorphosis?
axial complex (postanal tail, notochord, dorsal hollow nerve cord) is pulled into the body and reabsorbed the statocyst and ocellus are lost and the pharynx enlarges
after metamorphosis in the ascidian larvae, the pharyngeal slits subdivide repeatedly to produce small openings called?
stigmata
how does the tunicate trap food particles?
endostyle lines the pharynx and secretes mucus to trap food particles that pass through the incurrent siphon
In tunicates what exits through the excurrent siphon?
water and waste
T/F: All tunicate species are hermaphroditic (testes and ovaries)
TRUE!
solitary tunicates reproduce__________.
sexually
colonial species reproduce __________.
sexually and asexually (budding)
T/F: urochordates are the sister tata to vertebrates
TRUE!
dorsoventral inversion occurs between the ____________ and ___________.
cephalochordates and hemichordates/echinoderms
